R&D by Rowan, Parsuram and others

Log-grown Shiitake Mushroom Production

A project of The Otway Agroforestry Network and The Australian Master TreeGrowers

By Parsuram Sharma Luital and Rowan Reid

This project is supported by the Victorian Government Department of Innovation, Industry and Regional Development's Next Generation Food Strategy, 'Network to Success' Program

The cultivation of shiitake mushrooms on oak logs (Quercus spp) has been practiced for centuries in China and Japan. In fact, the word Shiitake literally means Oak-Mushroom. The fungus colonises dead timber then fruits in response to moisture. The mushrooms are harvested and currently sell for around $35 per kilo in the Melbourne wholesale markets. Field based production is now relatively common practice amongst North American forest owners. Inoculated logs are stacked in the forest to rest then repeatedly treated to stimulate fruiting. A single oak log can be produce mushrooms for up to 4 to 5 years.

We have undertaken research and field trials in Victoria over a number of years and have successfully produced Shiitake mushrooms on Eucalypt, Acacia and other log species. These notes provide information on log preparation, inoculation and care. The spawn has been source directly from Fungi Perfecti (see www.fungi.com).

IMPORTANT: DISLCAIMER and WARNING

The aim of these notes and our workshops is to share our experience and help participants set up small production trials. The authors, the Otway Agroforestry Network and the Master TreeGrower Program accept no responsibility for the productivity of the mycelium provided or the quality of the mushrooms produced.

Many types of fungus grow out of logs and it is possible your logs will produce fruiting bodies that are not Shiitake. Before handling or consuming any fungus you should be sure that it is Shiitake. Also be aware that some individuals may be allergic to Shiitake.

Shiitake is a type of White Rot Basidiomycota (mushroom type) fungi that decomposes cellulose and lignin. The fungus is native to China and widely grown commercially across temperate East Asia (Japan and Korea) and more recently in North America. There is some conjecture about whether or not Lentinula edodes is indigenous to Australia. The Interactive Catalogue of Australian Fungi (Royal Botanic Gardens Melbourne 2007) acknowledges that there is a closely related species (L. lateritia) found in Queensland and Tasmania (and PNG) that will hybridise with L. edodes. DNA research suggests the two species share the same ancestral roots.

The Spawn

The sterilized birch plugs are spirally grooved and fully colonized by pure mushroom mycelium. Dowels are inserted into a hole made with a 5/16th drill bit. Once the wood is fully colonized (typically 9-12 months) mushrooms will spring forth from cracks or channels in the wood. Generally, the best time of year to inoculate logs and stumps is in the Spring. Plug Spawn prefers to grow on hardwoods. Cutting your logs in the late Winter or early Spring helps to insure that they have a high sugar content, although this is not strictly necessary.

Freshly-cut logs should not be immediately inoculated; trees naturally produce anti-fungal compounds, which degrade in two to four weeks from cutting. The total number of mushrooms you can expect to get via log and stump cultivation will vary from log to log, and from season to season. Any outdoor mushroom cultivation project involves a number of variables; climate, species, sugar and moisture content of wood, consumption of mushrooms or mushroom mycelium by insects and other animals, quality of care and just plain old chance, to name a few. Due to the many and various contributing factors involved in this method of mushroom cultivation we cannot accurately predict the amount of mushrooms your Plug Spawn will produce.

Environmental Risk - Grower Responsibility

There is little information available on the environmental risk of introducing Lentinula edodes. Shiitake mushrooms are being grown commercially in Tasmania and New South Wales and there are no restrictions or controls on the methods being used. AQIS has been fully advised and have approved importation of the material. However, it is clear that the fungus can spread in woody material through direct contact and does grow on damp soil. Whilst the need for almost constant watering and protection from insects suggests that it is unlikely to fruit effectively in most environments in Victoria, it is prudent to adopt a risk minimisation approach.

The fungus can be killed by allowing it to dry out. We recommend growers inoculate the logs in a clean, dry area and that any old logs are left to dry out in full sunlight and then burnt. All mushrooms produced should be harvested. Until we know more, please do not stack or dispose of inoculated logs or mushrooms in a moist gully under or close to native forests particularly if the site is at risk of flooding.

Log Species

Research undertaken in the northern hemisphere suggests that Oak (Quercus spp) is the most productive and resilient species for log-based mushroom production. Characteristics that appear to be important are the ability of the log to retain moisture, the bark type and its persistence, and the starch content of the sapwood.

We have been trialling the production of Shiitake on English Oak (Quercus robur), Shining Gum (Eucalyptus nitens), Sugar Gum (E. cladocaylx), Poplar (Populus hybrid spp), Common Alder (Alnus glutinosa) and Blackwood (Acacia melanoxylon). Whilst all species did produce mushrooms only the Eucalypts and the Alder approached the success of Oak. All these species are hardwoods (Flowering species). We do not recommend conifer species (softwoods).

Characteristic of a good log:- sound, tight bark (gum bark eucalypts or tight barked oaks)- thick band of sapwood (from leafy tree)- diameter of at least 75mm and smaller than 250mm

Shiitake production on Shining Gum Logs in Melbourne.

Log selection and preparation:

The fungus lives off the starch and sugars in the sapwood. Rapidly growing healthy trees have a larger proportion of sapwood in the stem. We know the starch content of the sapwood of deciduous trees is greatest just prior to bud burst in spring. We think the same is true for evergreen plants. The logs should be cut about 2 to 4 weeks prior to inoculation and kept clean and moist..

Log size is important with respect to retaining moisture and ease of handling. We recommend logs of between 10 and 15cm in diameter and one metre long. Logs less than 10cm in diameter are susceptible to drying out and need to be treated carefully. Take care not to damage the bark. Do not paint the ends but please ensure the logs remain moist.

Inoculation

250 dowels is sufficient for about 10 logs. Use a 5/16" drill bit (or slightly larger) for drilling holes in the logs and insert the dowels. The holes should be spread around and along the log. Because the mycelium spreads freely up and down the log it is more important to spread the holes around the circumference. Melted paraffin wax or bees wax (the hotter the better) is used to seal the wound and the ends of the log. A video of this process will soon be available on this web site. All those on the information network will be advised.

Log storage and the spawn run

Once inoculated the logs should be stored off the ground on other logs or pallets for a few months in a shaded location. It is important to water 1-2 times a week. The mycelium spreads rapidly up and down the log from each point of inoculation results in wedges of infection though the sapwood. The mycelium does not infect the heartwood. Excess watering will encouragetrichoderma and other moulds growth on the surface of the logs which will compete with shiitake mycelium.

Initiating Fruiting

Depending on the species of logs, the first fruiting could take place between 6-9 months after inoculation. White mycelium growth appearing at the end of the log (as shown in the slides) is indicates the logs are ready for fruiting.

To initiate fruiting logs are soaked for 24 hour in the water before placing them in the growing area. After soaking, logs must be watered 3-4 times a day to initiate fruiting (pinning). Mushrooms will be ready 2-3 weeks from soaking and should be picked just before the lip of the mushroom turns outwards.

Pinning is the term used to describe the formation of small knots or bulbs on the bark. It is important to keep the logs moist now as the mushrooms develop. We have had problems with a small fruit-fly laying eggs in the gills of the mushrooms. These can be controlled using a pyrethrum spray but we suggest it may be best to protect the logs under a fine screen such as 'fly net' (fine material used to protect strawberries - available in a roll from garden supplies) to protect the mushrooms (available from large hardware shops). Possums will eat the mushrooms directly off the logs.

When to Harvest

The mushrooms are ready to harvest just before the lip uncurls. Twist the stalk at the base to remove taking care not to tear the bark or leaving a stump. If required a sharp knife can be used to cut the stem close to the bark.

Marketing:

If successful you will have enough mushrooms to keep you family and friends well supplied. We ask that you do not sell the produce from your logs without first ensuring (with us) that they are of the highest quality. We will provide information on product grading and packaging.